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GSM signal structure

Discussion in 'Electronic Design' started by Bob Graham, Jun 6, 2011.

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  1. Bob Graham

    Bob Graham Guest

  2. Bob Graham

    Bob Graham Guest


    Read that and still a bit hazy.

    Is the following interpretation correct please?

    The "900MHz" analog carrier is actually one of the 124 200KHz-spaced
    FDMA frequencies.

    As I understand, these are hopped to minimize interference. BTW what
    is the usual hopping rate?

    For TDMA, the selected carrier is pulsed at a 217Hz rep rate, with
    every 25th and 26th pulse omitted.

    The pulse duration is 0.5ms, meaning 8 separate real time messages can
    be fit into one TDMA slot. And riding within that time slot is the
    GMSK.

    Is that about it?

    Just wondering ... if all eight 0.5ms time slots are filled,
    presumably by 8 transmitters does the transmitted signal more or less
    resemble a continuous 900MHz carrier transmision? MSK aside of couse.

    Bob Graham
     
  3. Bob Graham

    Bob Graham Guest

    I hadn't read before that each transmitter could be assigned a space
    WITHIN one of the 8 slots, eg. by differing delay and amplitude as you
    mention.

    I thought each BTS just had a different slot, and the point of the low
    duty cycle time was to maintain amplitude, being signal strength..

    It would be appreciated if you can please explain your comment further
    so I do not misunderstand.

    Bob Graham
     
  4. Bob Graham

    Bob Graham Guest


    I looked and could not find anything about delays or amplitude
    variations within a _single_ TDMA time slot that you seem to have
    referred to.

    http://www.gsmfordummies.com/tdma/tdma.shtml

    Any chance of a more definitive answer?

    Bob Graham
     
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